The American ex-Marine who has been holed up in a Mexican prison in one of the most dangerous regions along the US-Mexico border is reportedly going to be released today, in time to return home for Christmas.

Jon Hammar's crime: He carried an antique gun across the border from Texas that, his family says, he was planning to use on a hunting trip in Costa Rica. But en route, he passed through Mexico, where despite record levels of violence, such arms are prohibited without permission from the Mexican government.

Hammar’s case came to light at a sensitive time in the gun-control debate. News broke of his August arrest in the wake of the Newtown tragedy, where an American took the lives of 20 elementary school students ages 6 and 7 last week, as well as six adults at the school and his mother.

Mexican gun laws

Hammar’s case has highlighted the stark difference between American and Mexican gun laws.

Hammar's mother, Olivia Hammar, told CNN that her 27-year-old son has been behind Mexican bars since August, after he stopped for gas in Matamoros, the notorious border town across from Brownsville, Texas, en route to Central America.

Guns are as easy to buy on the black market here, like any illegal good, but unlike in the US, Mexican citizens who seek to legally own a weapon must apply for one through the country’s department of defense. There are no gun stores; all weapons are purchased through the government, after extensive background checks.

Some of those weapons, ammunition, and defense mechanisms are confiscated and their owners arrested. But with impunity rates at over 90 percent, most of the perpetrators go free.

But the one sitting in Mexican jail for four months was this young American carrying an antique shotgun. And while he did break Mexican law, his plight also highlights the extreme challenges facing the Mexican justice system, as drug traffickers are employing combat-style weapons with little fear of getting caught, let alone languishing in jail.